Sealed relays are in common use for high-voltage switching, and are typically either evacuated to a high vacuum, or evacuated and backfilled with a dielectric gas such as sulphur hexafluoride. A typical relay of this style is shown in U.S. Pat. No. 3,411,118, and these devices are widely used in communications equipment, high-voltage power supplies, and other electrical apparatus requiring rapid and dependable switching of high currents at high operating voltages.
The relay of this invention is designed for operations at very high operating voltages such as 100 kilovolts, and is used, for example, in electrostatic systems where a "crowbar" circuit is needed. The relay may be operated in air, but is preferably immersed in oil to increase the breakdown voltage between external termainals. Finned ceramic spacers are also provided in the relay body to lengthen the breakdown path between the external terminals.
A particular advantage of the new relay arises from use of an axially movable armature and moving-contact assembly which is inserted within a cylindrical relay housing as one of the final steps of assembly. This construction minimizes need for relay adjustment before sealing, and simplifies assembly procedures for reduced manufacturing cost.
The relay is disclosed in the form of a single-pole double-throw (SPDT) switch with normally closed and normally open fixed terminals. The relay is deisgned, however, to be easily modified to a single-pole single-throw (SPST) configuration with either normally open or closed contacts.